Discovery Platform™

What is a Discovery Platform™?
A Discovery Platform™ is a modular, micro-laboratory designed and batch fabricated expressly for the purpose of integrating nano and micro length scales and for studying the physical and chemical properties of nanoscale materials and devices. Discovery Platforms ™ are standardized and packaged in a way that allows easy connections with external electrical, optical, and fluidic devices. The design and packaging will also allow direct access for a wide range of external diagnostic and characterization tools available at the Center for Integrated Nanotechnologies (CINT).

Discovery Platforms ™ are born from CINT’s need to provide a user friendly environment where a wide range of scientists from backgrounds and disciplines can explore the interplay between microfabricated architectures and nanoscale materials and devices. Discovery Platforms™ provide the opportunity to explore issues around the central theme of nanoscience integration. CINT recognizes the inherent difficulty associated with mastering the broad range of fabrication skills needed to conduct experimental research that crosses the boundaries between nano/micro domains. We also recognize that crossing these boundaries requires a level of investment that can stifle multidisciplinary team’s participation in these important research directions. The NSF sponsored National Nanotechnology Infrastructure Network will provide important training opportunities for those who wish to learn new fabrication approaches needed to cross these boundaries. CINT recognizes the NNIN’s primary role in training and offers Discovery Platforms ™ as a complementary approach whereby the microfabrication step is effectively done by CINT and offered through the User Program.

We anticipate that Discovery Platforms™ will serve a key role in building a coherent CINT user community. The consistency of experimental platforms should make it easier for various research scientists to compare results and build upon previous advances. Discovery Platforms ™ could also become a valuable teaching aid allowing students to explore the properties of nanoscale materials and learn about their connectivity with the micro and macroscale world.

When will Discovery Platforms™ be available?
Three types of Discovery Platforms™ are currently available. As described below they have been designed and developed by CINT scientists in collaboration with users. Fabrication of these platforms in the Sandia MESA (Microsystems and Engineering Sciences Applications) facility is now complete and initial experiments with CINT Scientists and users has commenced. A Hybrid Integration Tool is currently under development for use in experiments with the Discovery Platform™ chips to provide a common adaptive hardware and software environment. This integration tool will allow Discovery Platforms™ to operate as highly functional, user friendly laboratories. Users are encouraged to consider including Discovery Platforms™ in their CINT User Proposals for nanoscience research. CINT expects to continue developing new platforms in response to ideas from Users and CINT Scientists.

Cantilever Array Discovery Platform™

Contact: John Sullivan, jpsulli@sandia.gov, (505) 845-9496

Platform capabilities:
This platform is a multipurpose chip that is designed for experimenters wishing to perform research in the areas of nanomechanics, novel scanning probe technologies, chemical and biological sensing, magnetization studies, and physics of coupled mechanical systems. The platform is of the same physical dimensions as a standard AFM chip; therefore, it can be mounted on a standard AFM chip carrier and used in an AFM. Unlike an AFM chip, this platform has multiple cantilevers projecting from all edges, and it contains special test structures in the center. Some of the specific features of the platform are listed below:

Nanomechanics/Biomechanics: The platform includes arrays of polycrystalline silicon and silicon nitride cantilevers of different lengths and widths. As fabricated, the platform has openings in photoresist to permit the user to deposit their own material for testing. The cantilever structures are suitable for measurement of the modulus of unknown materials including nanostructured materials, for in situ film stress monitoring, and for studies of internal dissipation. In addition to cantilever structures, torsional oscillator structures and cantilevers with built-in in-plane force sensing are available. Torsional structures permit mechanics testing under shear loading conditions; the cantilevers with in-plane force sensing are suitable for probing soft or biological specimens. Located in the center of the platform chip are a series of in-plane load cells. These structures permit tensile or contractile loading to be performed on soft or biological specimens. In addition, a special mechanics structure is supplied that consists of a bridge over a silicon nitride membrane. The membrane can be pre-cracked to enable fracture mechanics testing. These structures also have Bosch-etched clearance holes completely through the chip, enabling the user to perform in situ TEM measurements simultaneous with mechanical loading.

Novel scanning probes: Many of the cantilevers emerging from the edge of the chip would be suitable for advanced or experimental scanning probe technologies. Some select cantilevers are pre-patterned with openings in photoresist to enable the user to deposit metal lines down the cantilever for resistive heating, thin film resistor thermometry, scanning electrical conduction measurements, etc. Other cantilevers have an opening in photoresist at the extreme tip to enable the deposition of a magnetic film or magnetic nanoparticles for magnetic force sensing. The cantilevers are fabricated from both polycrystalline silicon and silicon nitride with a variety of lengths and widths (hence, a range of force constants).

Physics and sensing with arrays: Several regions of the chip have dense and sparse arrays of similar-sized cantilever oscillators of both polycrystalline silicon and silicon nitride. These arrays can be functionalized and used for chemical or biological molecule sensing. In addition, the coupled arrays can be used for physics studies of collective behavior associated with coupled mechanical oscillators.

Magnetization studies: In addition to cantilevers that allow the user to deposit magnetic particles at the tip, the platform contains spring-suspended plates that are suitable for supporting a user-deposited material for magnetization testing. Polysilicon resistors for thermometry, polysilicon electrodes for capacitance sensing of displacement, and a Bosch-etched clearance hole for optical detection of displacement are also provided.

Other: A variety of other structures are provided, including arrays of cantilevers over silicon for measurement of surface adhesion forces, bridge structures that may be probed by nanoindentation to permit testing of materials at high stresses and strains, and sacrificial beams and bridges fabricated out of silicon dioxide that enable the user to deposit and test their own free-standing material.

Fundamental science questions that could be addressed by this platform include:

• What are the deformation mechanisms (elastic/plastic behavior) in nanoscale and nanostructured materials?
• What is the collective behavior of a system of oscillators when the interaction is increased or defects or mechanical noise are introduced?
• What is the response of the cytoskeleton of a cell to local compression and traction & how does the cell accommodate the stress?
• What controls energy dissipation in small crystalline and amorphous mechanical resonators?
• What is the magnetization of collections of small particles near the superparamagnetic threshold?
• What are the attractive and repulsive forces at surfaces between dissimilar materials?
• What is the spatial variation of thermal conductivity/magnetization/modulus/etc. in nanostructured materials?

Electrical Transport and Optical Spectroscopy Discovery Platform™

Contact: Mike Lilly, mplilly@sandia.gov, (505) 844-4395

Platform capabilities:
The Electrical Transport and Optical Spectroscopy Discovery Platform™ enables fundamental investigations of the optical, electronic, and transport properties of a wide variety of nanomaterials. The platform is designed as a standard substrate with well measured characteristics for a wide variety of nanoscience experiments.  There are capabilities for depositing a nanomaterial on top of gates for electrical contact and control, and the platform also provides a common set of gates, alignment markers, contact pads and on-chip sensors for further processing with photolithography or electron beam lithography.  The active regions consist of gate structures separated from a doped Si substrate by silicon nitride and silicon oxide insulators.  The platform seeks to provide a well-characterized means of interfacing with the nanodomain while simultaneously offering considerable versatility for optical and transport measurements. In addition, the platform is compatible with other measurement techniques including scanning probes such as AFM, STM, NSOM, electron beam characterization tools such as TEM and SEM, and cryostats and magnetic fields. Additional on-chip capabilities include temperature measurement and signal amplification. To accommodate different experiments, the discovery platform is divided into four 1cm x 1cm quadrants (see figure), each with different top gate designs. Each quadrant has a pair of diodes: one is an in situ thermometer and the other a light sensor.

Quadrant I: In this quadrant 64 contact pads surround a 100 mm x 100 mm blank space planned for user-defined electron beam lithography or focused ion beam (FIB) direct-write structures.  The quadrant should have broad appeal even to device researchers as it provides an excellent starting point for specialization.

Quadrant II: This quadrant is designed to offer a suite of electrodes for a variety of transport measurements coupled with backgating which will provide the option for electrostatic doping studies. There are four sets of lines and spaces (25, 2.5, 0.35 and 0.18 mm pitch) and three sets of cross patterns (2.5, 0.35 and 0.18 mm separation).  In these regions, nanostructures can be deposited, patterned, contacted and back-gated.

Quadrant III: Quadrant III uses four patterns from Quadrant II in a smaller form factor for instruments with limited space (TEM, pulsed magnet field systems, etc.).

Quadrant IV: This quadrant is designed for broadband optical spectroscopy measurements, and other optical measurements as well (e.g. Raman, ultrafast, etc). It has interdigitated fingers (grid spacing about 200 microns) designed for field effect doping of organic films.  Application of a voltage to the doped substrate enables the user to alter the charge density in the nanostructure of interest. 

Fundamental science questions to be addressed by this platform include:

• Electronic transport in molecules, nanowires, and composite nanostructures (e.g. semiconductor or metal nanoparticle arrays).
• Transduction of molecular scale events to measurable electronic or optical signals.
• Electrostatic doping of organic thin films and composite nanostructures.
• Correlation studies of nanostructure and nanoscale-to-microscale functionality.

Microfluidic Synthesis Discovery Platform™

Contact: Nelson Bell, nsbell@sandia.gov, (505) 844-6234

Platform capabilitie:
This platform is a microfluidic reactor for performing kinetic analysis of the reaction pathways for the preparation of organic molecules and highly monodisperse nanoparticle materials. The network has the capability to control both flow and thermal parameters of the synthesis reaction. The system will have operating temperatures ranging from room temperature to 400 °C, with the control of the thermal profile of the reaction.

Nanomaterial synthesis is encumbered by the variation in particle properties resulting from nucleation and growth mechanisms. The distribution of size and shape of nanoparticles impact optical, electronic, magnetic and catalytic properties of nanomaterials. In order to develop a greater understanding of these processes, fundamental study of the reaction mechanisms involved in creating nanomaterials is needed. Microfluidic systems allow for rapid thermal and mass transfer and have several key advantages in nanoparticle production such as (1) rapid heating or cooling of the thermal profile and control over the thermal gradient or temperature over the flow profile, (2) rapid and efficient mixing of reagents, (3) operation under the continuous flow regime with the capability for staged reagent addition, (4) continuous variation in the composition of the reaction mixture through injection rate control.

This platform enables the study of the fundamental pathways for understanding size and shape controlled synthesis of nanoparticles. The reaction is optically accessible to monitor the spectral properties of the reactant stream, providing in situ characterization of the reaction process. In addition, the network incorporates heating elements and thermistor sensors for exact monitoring of the thermal profile of the reactant stream, with the potential to control nucleation and growth stages. In addition, the discovery platform has the capability to perform dielectric spectroscopy between reaction stages, with the potential to measure particle size independently of optical responses. Additives or growth modifiers can be injected at two stages in the reaction, giving the ability to perform sequential growth or shell formation of a second material. The system has an operating temperatures ranging from room temperature to 400°C, with control over the thermal profile along the reaction channel.

In the synthesis of nanomaterials by solution chemistry, some of the fundamental questions that this platform will address are:

• What are the values of the thermodynamic parameters that control nanoparticle synthesis? (enthalpy, entropy, surface energy)
• What is the mechanism of nanoparticle nucleation and growth? (i.e. diffusion, surface reaction, self-assembly)
• What is the mechanism of the formation of shell layers around a core nanoparticle?
• How does the surfactant composition relate to the quantum confinement properties of nanoparticles?
• What are the ripening mechanisms of nanoparticles?

Discovery Platform™ Hybrid Integration Tools

The Discovery Platform™ Hybrid Integration concept is designed to create unique intra-laboratory research tools that will integrate highly functional on-chip laboratories in a common, adaptive hardware and software environment.  These tools are designed to accommodate a wide range of Discovery Platforms™ that allow a new “instrument” to be created for each new chip that is inserted into the device.  The implementation of this concept exploits evolving technologies to create a new class of field programmable hybrid instruments that interact in a dynamic research environment.